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Quick questions (all readings at the terminal posts of the battery itself)
Battery voltage w/o engine running is .....
The reading at the jump points under the hood...
With engine running at idle...
With engine at 2500 RPM....
These test will expose battery issues and charging issues.
On the running test perform with all accessories off, then everything on including defroster. Report back your results.
Note: When batteries fail, some will collapse internally and short out causing a constant drain on the battery. When you charge it it will over heat to the point of KABOOM. Never charge a DEAD battery (one below 10 volts) in a car.
Your battery showing 12.1-12.5 at rest is good but the real question is what happens when you load it w/o engine running. This test shows capacity of the battery to store and hold amps. If you turn on the headlamps and HVAC fan to high, where does the voltage reading go? Down below 11.0V? Lower?
If you have one of these you will be able to see the actual amp capacity of the battery and the alternator. Without it is all a big SWAG.
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2005 X5 4.8IS
The Blue ones are always FASTER....
Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green
Last edited by StephenVA; 08-27-2018 at 04:39 PM.
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